How can I restore the app I deleted Data on iPhone?

If your device has not yet completed a backup since you deleted the app, you can restore your iPhone from that backup and the app along with the data would still be there. Otherwise the data stored on the device is deleted with the app and not recoverable. Some apps will store data on their servers or give you the option to store data in iCloud, so depending on the app, it may be in one of those locations.

Your welcome

Some references for you by Apple:

Delete [and restore] built-in Apple apps from the Home screen on your iOS 14 or iPadOS device or Apple Watch - Delete built-in Apple apps from your iPhone, iPad, or Apple Watch - Apple Support

- When you delete a built-in app from your device, you also delete any related user data and configuration files.

Click on this link to learn how to remove apps from iPhone -->

Remove or delete apps from iPhone - Apple Support

- Remove an app from the Home Screen: Touch and hold the app on the Home Screen, tap Remove App, then tap Remove from Home Screen to keep it in the App Library, or tap Delete App to delete it from iPhone.

- Delete an app from the App Library and Home Screen: Touch and hold the app in the App Library, tap Delete App, then tap Delete. (See Find your apps in the App Library.)

- Note: When you remove a built-in app from your Home Screen, you also remove any related user data and configuration files.

How to check the storage on your iPhone and iPad - Apple Support

- Offload the app, which frees up storage used by the app, but keeps its documents and data.

- Delete the app, which removes the app and its related data.